I've looked at my IPC and type certificate and nowhere can I see the type of material used to cover the original seats etc specified. So, why do you have to prove that the material used to reupholster your seats has to comply with any 'burn' requirements?
In the same way that the IPC does not give you the aloy of aluminum used to make a wing rib, the IPC will not tell you the material used in the upholstery, or it's characteristics (including burn). The SRM does in many cases tell you the alloy to use for a repair for the aluminum. That's different. If the aircraft manufacturer had wanted to, they could tell you in the maintenance manual where to source approved replacement upholstery material, in the same way that they will tell you where to buy adhesives, lubricants and special tools for example. I've never seen materials in manitenance manuals or IPCs that way.
Once you install a product which is not identified in the IPC, approved or "specified" data is required for a design change. In some cases, AC43.13-1B would be appropriate specified data, but not for interior repairs, they would require an approval.
Repair vs replacement is simple: If you are installing a part listed in the IPC for that aircraft, and you have a certificate of airworthiness (in the format appropriate for an individual part) for that part, you are replacing. If you are installing something not listed in the IPC, or something for which you do not have a C of A, you are repairing and probably modifying too - approval required.
And.... Beware of TSO. The fact the an item is TSO'd (tire for example) does not approve it for intallation on a particular aircraft. It still must be specifically approved for installation on that aircraft by IPC or STC. Why, you ask? Tire example: 6.00-6, 4 ply is a main wheel tire for many light aircraft. 6.00-6, 8 ply is a nose wheel tire for a much heavier and faster aircraft. Either would fit in the position of the other, but neither would be approved or safe in the reversed application.
Pilot DAR